Thunderbird screen fonts too small on Macbook Pro
 

I am running Thunderbird 52 on an Apple Macbook Pro. The fonts and screen details are extremely small and hard to read. When I compose a message everything is a good size.

I have the Theme Font & Size Change Add-On installed but I I can't find in the drop down menus, etc. where to get into the add-on to make any adjustments.

The add on tells me to click the Status Bar Button but I can't find the button. It also tells me to go into the Tools menu but when I do the add-on is not shown.

Can anyone help me please? Thanks.